The Bell System Practices, commonly known as BSPs, were the official technical manuals and operational standards for the North American Bell System. For most of the 20th century, these documents served as the definitive authority for the entire Bell System and later AT&T until its antitrust breakup in 1983.
The goal of the BSPs was to ensure that every task was performed using the exact same methods, tools, and safety standards, regardless of the location.
BSPs are identified by their "section" which post 1960 is 9 digits in 3 parts (eg: 555-025-600) which represent the following:
- The Division (first 3 digits)
The first three digits represent the Division. This is the broadcast category of equipment or department and also identifies which shelf or library a section belongs to. - The Subdivision (middle 3 digits)
The middle three digits represent the Subdivision and narrows the scope from a broad category to a specific family of equipment. For example, while 555 covers the Definity and other PBXs, subdivision 006 (555-006) covers the call accounting systems. - The Key (last 3 digits)
The last three digits represent the individual document within the series.
We have an extensive collection of BSPs from the 1920s many of which have been provided by The Telecom Archive. You can explore them below, or use the search function in the top navigation to look for something more specific. If you have any BSPs that are missing that you would like to contribute please get in touch!
Divisions 000-019 – Indexes and General Information
| Division | Description |
|---|---|
| 000 | General Information, Documentation, and Specifications. |
| 001 | Reserved for Company - Issued |
| 002 | Administrative Practices |
| 004 | Number Assignments to be Made Locally |
| 005 | Abbreviations, Definitions, Drawing, Requirement Tables, Specifications, and Symbols |
| 006 | Graphic Media Systems and Standards |
| 007 | Information Systems |
| 010 | General Methods |
| 015 | Work Units |
Divisions 020-199 – Apparatus, Tools, Gauges, Test Equipment, Power
| Division | Description |
|---|---|
| 020 | General Information |
| 024 | Amplifiers, Controllers, Control Units, Regulators, Electron Tubes |
| 026 | Circuit Breakers, Compensators, Contactors, Control Panels, Fuses and Mountings, Magnetic Switches, Selectors and Starters |
| 028 | Autotransformers, Bells, Buzzers, Dials, Dial Adapters and Mountings, Gongs, Head Telephone Sets, Headsets, Potentiometers, Rheostats, Ringers, and Sounders |
| 030 | Calculagraphs, Call Timing Switch, Cameras, Clocks, Counters, Photo Processors, Registers, Selector Multiple Designation Cards, Switches, Tape Printers, Ticketers, Timers, and Time Stamp |
| 032 | Capacitors, Connectors, Cords, Core Reels, Diodes, Drops, Jacks, Keys, Lamps, Plugs, Resistors, Signals, Sockets, Thermistors, Transistors, and Varistors |
| 034 | Distributors, Regenerators |
| 040 | Relays |
| 065 | Miscellaneous Equipment and Materials |
| 067 | Concentrators |
| 069 | Apparatus and Equipment Cabling, Wiring, Cleaning, Treating, etc. Methods |
| 074 | Tools |
| 075 | Tools and Materials (Common Usage) - Maintenance |
| 076 | Tools and Materials - Switching Systems and Power Maintenance, Selection and Use |
| 080 | Tools and Materials - Customer Equipment |
| 081 | Tools and Materials - Outside Plant |
| 084 | Gauges, Electrical Indicating Instruments, and Meters |
| 085 | Gauges (Common Usage) - Maintenance, Selection, and Use |
| 100 | Test Equipment, Electrical Indicating Instruments and Meters (Common Usage) Maintenance, Selection, and Use |
| 102 | Test Equipment, Electrical Indicating Instruments and Meters (Switching Systems and Power) - Maintenance, Selection and Use |
| 103 | Transmission Test Equipment |
| 104 | Radio Test Equipment |
| 105 | PBX and Station Test Equipment |
| 106 | Electrical Test Equipment - Outside Plant |
| 107 | Data and Teletypewriter Testing |
| 155 | Alternators, Engine-Alternators, Gas Turbine Alternators, Tone Alternators, Tone Machines, Ringing and Coin Control Generators, Charging Generators, and Motor-Generators |
| 157 | Batteries |
| 159 | Engines and Engine Sets, Motors, Dynamotors, and Drives |
| 161 | Speed Reduction Units, Converters, Inverters, Air Dryers, Compressors, Compressor-Dehydrators, Waveguide Dehydrators, Exhauster Sets, Fans, Tube Cooling Systems, Ventilating Equipment, Call Announcer Machines |
| 163 | Interrupters, Ringing Machines, and Pole Changers |
| 164 | Powerware (Post-Divestiture) |
| 167 | Power Plants, Power Units, and Power Supplies |
| 169 | Rectifiers and Filament Supplies |
| 171 | Miscellaneous Power Circuits and Equipment |
| 179 | Signaling Circuits and Associates Ringer Circuits |
| 190 | Operations Support Systems Operation, Maintenance, and Administration |
| 193 | Computer Applications Software Support Products |
Divisions 200-299 – Switching Systems
| Division | Description |
|---|---|
| 200 | Switching Systems |
| 201 | Central Office Supplemental Information |
| 205 | Automatic Data Test Circuits |
| 210 | Service Observing and Plant Traffic Desks |
| 211 | No. 1, 3, 5, and 6 Toll Offices, No. 1, 3, 5, and 6 Toll Switchboards and No. 6A Teletypewriter Switchboards |
| 212 | No. 4A and 4M Toll Switching Systems |
| 213 | No. 1 Accounting Center - Automatic Message Accounting System |
| 215 | Panel Offices |
| 216 | No. 1 Crossbar Offices |
| 218 | No. 3, No. 5, and No. 5A Crossbar Offices |
| 220 | Crossbar Tandem Offices |
| 225 | Testing Information Applying to Specific Step-By-Step and Community Dial Offices |
| 226 | Equipment Common to More Than One Type - Step-By-Step and Community Dial Office |
| 227 | General and Testing Information Applying to Intertoll Dialing, CAMA, AMA, ANI, TOUCH-TONE Calling and Common Control Equipment - Step-by-Step Offices |
| 230 | Data Network Systems |
| 231 | 1 and 1A ESS Switches |
| 232 | 2ESS |
| 233 | 3ESS |
| 234 | 4ESS |
| 235 | 5ESS-2000 Switch Digital Switching System |
| 240 | No. 101 Electronic Switching System |
| 241 | Nortel Switches |
| 250 | Operator and Traffic Service Positioning Systems |
| 252 | Traffic Management Systems |
| 254 | Stored Program Control |
| 255 | Processor Controlled and Ancillary Systems DATAKIT 10A Remote Switching, 1 Packet Switching, And Database Systems |
| 256 | Common Channel Signaling System (CCSS) |
| 270 | Advanced Intelligent Network (A-I-Net)/Advanced Network Services (ANS) Products |
| 275 | Internet Protocol Multimedia Subsystem (IMS) Solution |
Divisions 300-399 – Transmission, Signaling Systems, and Testing
| Division | Description |
|---|---|
| 300 | Transmission Systems and Testing Cross-Reference List |
| 301 | Transmission Performance Measurement Plans |
| 302 | Transmission Test Line Directories |
| 304 | Transmission Data |
| 309 | Switched Services Networks |
| 310 | Non-switched Special Services Systems |
| 311 | Switched Special Services Systems |
| 312 | Private Line Data Systems and Services |
| 313 | Voice, Data, and Video Transmission Systems |
| 314 | Digital and Analog Data Transmission Systems |
| 318 | Television Systems |
| 320 | Program Transmission Systems and Services |
| 330 | Cable and Open-Wire Testing and Trouble Location Methods |
| 331 | Transmission and Noise Testing, Central Office PBX Customer Lines and Equipment |
| 332 | Voice-Frequency Telephone Repeaters, Pilot Wire Regulators, Echo Cancellers/Suppressors, Composite Sets, and Associated Equipment |
| 333 | Interoffice Signaling Systems and Testing |
| 356 | Broad Band Carrier - Common Equipment Components Type J, K, and L Carrier Telephone Systems, Analog Multiplex Terminal Equipment |
| 357 | Wire Line Entrance Links and Broadband Entrance Links and Interconnection |
| 359 | L3, L4, L45, L5, and L5E Carrier |
| 361 | Service Center Tests Type N, O, and ON Carrier Systems |
| 362 | Type N, O, and ON Carrier Telephone Systems and Associated Equipment Components |
| 363 | Loop Transmission Systems |
| 365 | Digital Transmission Systems |
| 371 | Broadband Restoration |
Divisions 400-499 – Radio, Wiring, and Special Services
| Division | Description |
|---|---|
| 400 | Radio Administration |
| 401 | Cellular Telecommunications Systems |
| 402 | Antennas, Transmission Lines, and Waveguide |
| 403 | Coastal Harbor, High Seas, Overseas, And Emergency Point-to-Point Radio |
| 404 | Manual Mobile Radio |
| 405 | MJ, MK, and ML Mobile Radiotelephone |
| 406 | Air Ground Radio |
| 408 | Narrowband Auxiliary Channel And Other Non-Lucent Technologies Radio Equipment And TV Off-The-Air Pick-Up Services |
| 409 | TE, TJ, TL, and TM Microwave Radio |
| 410 | TD-2 Microwave Radio |
| 411 | TD-3 Microwave Radio |
| 415 | TD-3D Microwave Radio |
| 417 | 3A-Radio Digital Systems |
| 420 | Microwave Radio - Common Equipment |
| 421 | FR/DR Microwave Radio System |
| 422 | Common Microwave Radio |
| 460 | General Information, Customer Information, Customer Equipment |
| 461 | Wiring and Cabling Customer Equipment |
| 462 | Drop and Block Wiring Dedicated Plant and C Rural Wire |
| 463 | Miscellaneous Station Apparatus for use With Station Installations Customer Equipment |
| 469 | Administrative Information, Customer Equipment |
| 471 | Other Common Carriers |
| 473 | Intra-PBX Protection of Service, Code Calling, Customer Training, Dispatching, Emergency Reporting, Interface Trunks, Message Waiting, Recorded Telephone Dictation, Telephone Answering Systems, and Transmitter Transfer Customer Equipment |
| 475 | Call Distributing Systems, Information Desks, and Order Turrets Customer Equipment |
| 476 | Force Administration Data System (FADS), Automatic Call Distributing Systems (ACD) No. 2A, 2B, and 3A, and Call Distributing System No. 4A Customer Equipment |
| 480 | Private Service Systems Customer Equipment |
| 481 | Teleconferencing Services |
Divisions 500-599 – Small Business Systems, Station Equipment, Private Branch Exchanges, Data Services, and Teletype
| Division | Description |
|---|---|
| 500 | General Considerations for Station Installations Customer Equipment |
| 501 | Business Systems and Station Equipment Station Set Components, Customer Equipment |
| 502 | Common Battery Station Sets |
| 503 | Modular Station Sets |
| 504 | Selector Consoles, Telephone Consoles, Apparatus Units |
| 506 | Small Business Systems and Station Equipment, Public Telephone Sets |
| 508 | Public Telephone Enclosures and Miscellaneous Accessories |
| 510 | Station Sets and Coin Collectors Local Battery and Magneto |
| 512 | Automatic Dialers, Station Keys, Key Equipment Interphone Systems, Modular Units, Speakerphone Systems and Conference Sets |
| 514 | Telephone Answering Sets and Systems and Announcement Sets and Systems |
| 518 | Key Telephone Systems, Communications Systems, and Switching System No. 400 |
| 529 | Station Apparatus and Equipment Intended Solely for Specially Engineered Lines Not For General Telephone Use |
| 533 | Large Business Systems (PBXs) Customer Premises Systems and Customer Services Provided by ESS Switches |
| 534 | Sections Applying to More Than One PBX - Series 500, 600, 700, and 800 Series Manual and Dial PBX |
| 536 | 500 Series PBX |
| 538 | 600 Series PBX |
| 540 | Sections Applying to More Than One 700 Series PBX |
| 541 | 700C and 710C PBX |
| 542 | 701 and 711 Type PBX |
| 543 | 702A PBX |
| 546 | 740-Type PBX |
| 548 | 750A PBX |
| 550 | 755A PBX |
| 551 | 756A, 757A, 758A, 758B, 758C, 761, and 770 PBX |
| 552 | Non-Bell Type PBX |
| 553 | 800 Series PBX |
| 554 | Business Communications Systems - DIMENSION PBX |
| 555 | Definity Communications Systems 25, 75, 85, Merlin Legend and Common Systems, Information Systems Network, and Premises Distribution System |
| 560 | Data Systems Production, Cross Production |
| 562 | StarServer |
| 570 | Teletypewriter General Information - Misc. Apparatus and Auxiliary Equipment |
| 572 | 14, 15, 19 and 20 Type Teletypewriters |
| 573 | 28-Type Teletypewriters |
| 574 | Teletypewriter 30 Series and Teleprinters |
| 578 | Miscellaneous Data Terminals |
| 579 | Teletypewriter Field Maintenance/Field Installation Practices |
| 580 | Teletypewriter Switching Systems |
| 581 | Teletypewriter Selective Calling Systems |
| 582 | Data Communications Equipment Systems, Services, and Components |
| 585 | Computer Products Adjunct Processors and Services For Business Communications Systems |
| 590 | Data Systems - General Information |
| 591 | 100 Series Data Sets and Associated Services |
| 592 | 200 Series Data Sets and Associated Services |
| 593 | 300 Series Data Sets and Associated Services |
| 594 | 400 Series Data Sets and Associated Services |
| 595 | 500-Type Service Units and Sets for Digital Systems/Services |
| 596 | 600 Series Data Sets and Associated Services |
| 598 | 800 Series Auxiliary Equipment |
Divisions 600-699 – Outside Plant, Test Center Operation, and Loop Assignment
| Division | Description |
|---|---|
| 620 | Outside Plant, General |
| 621 | Pole Lines |
| 622 | Conduit, Manholes, and Cable Vaults |
| 623 | Open Wire |
| 624 | Multiple Wire |
| 626 | Cables, Wire, and Apparatus |
| 627 | Aerial, Block, and House Cable |
| 628 | Underground Cable |
| 629 | Buried Plant |
| 631 | Cable Terminals |
| 632 | Cable Splicing |
| 633 | Splice Closures |
| 634 | Electrical Cable Testing and Identification |
| 636 | Main Frame Terminations and Connectors |
| 637 | Cable Pressure Systems |
| 638 | Electrical Protection and Bonding |
| 640 | Outside Plant Carrier Apparatus |
| 642 | Dedicated Plant |
| 644 | Upkeep |
| 649 | Outside Plant Construction Equipment |
| 650 | Converged Stackable Switch (Post-Divestiture) |
| 660 | Test Center Operation |
| 662 | Cable and Local Test Desks and Local Test Cabinets |
| 664 | Testboards for Other Than Special Services |
| 666 | Testboards and Test Positions For Special Services |
| 667 | Switched Maintenance Access and Servicing Systems |
| 668 | Data Test Centers |
| 670 | VPNmanager (Post-Divestiture) |
| 680 | Loop Assignment Distribution Service |
| 682 | Plant Assignment Trunk Plant and Special Services |
Divisions 700-799 – Motor Vehicles, Bogen Communications, Materials Management, Business Information Systems, Engineering, and Common Language
| Division | Description |
|---|---|
| 701 | Bogen Communications Products (Post-Divestiture) |
| 720 | Motor Vehicles and Construction Equipment |
| 740 | Materials Management and Supplies General Information |
| 741 | Products, Supplies, Systems and Services Supporting Functions |
| 742 | Supply Controls |
| 743 | Supply Ordering |
| 744 | Supply Distribution |
| 745 | Material Returns |
| 746 | Supply Functions, Miscellaneous |
| 747 | Shipping Logistics |
| 748 | Stocking Procedures |
| 749 | Plug-In Inventory Control |
| 750 | BISP General |
| 751 | Business Information Systems - COMMON LANGUAGE |
| 752 | Software Product Specifications |
| 753 | COSMOS Software |
| 759 | Business Information Systems - Time Share Program |
| 760 | Building Engineering |
| 770 | Building Operation |
| 780 | Network Services Methods |
| 781 | Technical Planning |
| 790 | Engineering Administrative Practices |
| 795 | Common Language |
Divisions 800-899 – Equipment Design, Transmission Engineering
| Division | Description |
|---|---|
| 800 | Cross-Reference Lists, Floor Plan Data Sheets, Administrative Information, General Equipment Requirements For Installation and Manufacturing, And General Performance Requirements |
| 801 | Equipment Design and General Requirements - Engineering Information - Common Systems |
| 802 | Equipment Design and General Requirements - Engineering Information - Power Systems |
| 803 | Grounding Systems |
| 804 | Equipment Design and General Requirements - Engineering Information - Toll Systems |
| 806 | Equipment Design and General Requirements - Engineering Information - Radio Systems and Television Systems |
| 807 | Equipment Design and General Requirements - Engineering Information - Data Systems |
| 809 | Equipment Design and General Requirements - Engineering Information - Private Branch Exchange Systems |
| 811 | Equipment Design and General Requirements - Engineering Information - Private Service Systems |
| 812 | Equipment Design and General Requirements - Engineering Information - Station Systems |
| 814 | Equipment Design and General Requirements - Engineering Information - Step-by-Step Systems |
| 815 | Equipment Design and General Requirements - Engineering Information - Panel Systems |
| 816 | Equipment Design and General Requirements - Engineering Information - No. 1 Crossbar System |
| 817 | Equipment Design and General Requirements - Engineering Information - Tandem Crossbar System |
| 818 | Equipment Design and General Requirements - Engineering Information - No. 4 Type Toll Switching Systems |
| 819 | Equipment Design and General Requirements - Engineering Information - No. 3, No. 5, and No. 5A Crossbar System |
| 820 | Equipment Design and General Requirements - Engineering Information - 1, 1A, 2, 2A, 3 and 4ESS and 5ESS 1A Processor |
| 821 | Equipment Design and General Requirements - Engineering Information - Traffic Service Systems |
| 822 | Equipment Design and General Requirements - Engineering Information - Traffic Management Systems |
| 823 | Equipment Design and General Requirements - Engineering Information - No. 101 Electronic Switching System |
| 824 | Equipment Design and General Requirements - Operations Support Systems |
| 825 | Equipment Design and General Requirements - Common Channel Signaling System (CCSS) |
| 845 | AT&T Private Pay Phones |
| 846 | AT&T Private Pay Phones Plus |
| 851 | Special Services Systems - Engineering Design Information |
| 852 | Exchange Area and Operator Services Transmission |
| 853 | Toll Transmission |
| 855 | Carrier Engineering |
| 856 | Mechanized Transmission Engineering Tools |
| 857 | Program and Television Engineering |
| 859 | Signal Transmission - Engineering Considerations |
| 860 | PICTUREPHONE Service Transmission Engineering |
| 865 | Transmission Maintenance Systems Engineering |
| 870 | Electrical Noise Engineering |
| 873 | Inductive Coordination |
| 874 | Power Supply Systems Data |
| 876 | Electrical Protection Practices |
| 877 | Corrosion Practices |
| 880 | Data Communications Engineering |
Divisions 900 – General Descriptive Information, Outside Plant Engineering, Radio Engineering, and User Product Documentation
| Division | Description |
|---|---|
| 900 | Outside Plant Engineering - General Information |
| 915 | Outside Plant Engineering - Facility Design - Systems |
| 918 | Outside Plant Engineering - Facility Design - Applied Protection |
| 936 | Outside Plant Engineering - Management - Controlling |
| 937 | Outside Plant Engineering - Management - Coordinating |
| 940 | Radio Engineering |
| 951 | Equipment Common to More Than One Type of System - General Descriptive Information |
| 953 | Switchboards, Desks and Associated Equipment - General Descriptive Information |
| 955 | Step-By-Step and Community Dial Offices - General Descriptive Information |
| 957 | No. 1 Crossbar Offices - General Descriptive Information |
| 958 | No. 5 Crossbar Offices - General Descriptive Information |
| 960 | Crossbar Tandem Offices - General Descriptive Information |
| 964 | No. 4 Toll Switching System - General Descriptive Information |
| 966 | ESS Switch - General Descriptive Information |
| 970 | Transmission Systems - General |
| 972 | Teletypewriter and Data Systems - General Descriptive Information |
| 975 | Signaling Systems - General Descriptive Information |
| 981 | Equipment on Customer's Premises (Special Services and Private Branch Exchanges) - General Descriptive Information |
| 982 | Private Service Systems - General Descriptive Information |
| 984 | Outside Plant Engineering - Management - Coordinating |
| 999 | Product Documentation - User |
Pre-1960s Series BSPs
| Division | Description |
|---|---|
| Division 950 | General Descriptive Information |
| Division A | Central Office Maintenance |
| Division AA | Equipment Engineering |
| Division AB | Transmission Engineering and Data |
| Division AG | Outside Plant Engineering |
| Division B | Private Branch Exchange Installation and Maintenance |
| Division C10 | Station Installation and Maintenance - General / Components |
| Division C20 | Station Installation and Maintenance - Wiring |
| Division C30 | Station Installation and Maintenance - Apparatus - Dial and Manual Stations |
| Division C40 | Station Installation and Maintenance - Connections - Dial and Manual Stations |
| Division C50 | Station Installation and Maintenance - Other Apparatus and Connections |
| Division C60 | Station Installation and Maintenance - Inspection, Testing and General Trouble Locating Methods |
| Division C70 | Station Installation and Maintenance - Minor and Major Station Systems (Key Systems) / Tools, Gauges, and Test Sets Methods |
| Division C80 | Station Installation and Maintenance - Government Systems |
| Division C85 | Station Installation and Maintenance - Common Systems |
| Division D | Recovery and Repair |
| Division E | Toll Test Room Operation |
| Division F | Local Test Room Operation |
| Division G00 | Outside Plant Contruction and Maintenance - Index and Plan |
| Division G10 | Outside Plant Construction and Maintenance - General |
| Division G20 | Outside Plant Construction and Maintenance - Pole Lines |
| Division G30 | Outside Plant Construction and Maintenance - Wire |
| Division G40 | Outside Plant Construction and Maintenance - Conduit |
| Division G50 | Outside Plant Construction and Maintenance - Cable |
| Division G60 | Outside Plant Construction and Maintenance - Terminals |
| Division G70 | Outside Plant Construction and Maintenance - Splicing and Testing |
| Division G80 | Outside Plant Construction and Maintenance - Tools |
| Division G90 | Outside Plant Construction and Maintenance - Motor Vehicles and Construction Apparatus |
| Division H10 | Buildings - General |
| Division H20 | Buildings - Planning |
| Division H30 | Buildings - Construction and Mechanical Plant |
| Division H40 | Buildings - Fire Protection |
| Division H50 | Buildings - Operation and Maintenance |
| Division J | Motor Vehicles and Construction Apparatus |
| Division K | Transmission Testing |
| Division M | Plant Assignment |
| Division P | Teletypewriter and Data Stations |
| Division R | Radio Systems |
